"It's still very important to fully review the findings from the State Services Commission's investigation into allegations of wrongful expenditure of public money by the DHB's former chief executive, Dr Nigel Murray.
"I believe that Mr John Ombler QSO will provide an interim report early in 2018.
"I am unable to comment further at this stage while the investigation is still underway."
Simcock said he was very sad to be leaving the Waikato DHB, but believed his resignation was needed so the organisation could move forward.
"I am satisfied that at all times the board and I acted responsibly and without reproach at every stage. We followed agreed DHB guidelines and processes throughout to ensure good governance and that the best interests of Waikato DHB were upheld without question.
"Nonetheless, despite our best intentions and actions, a lot of the hard work and goodwill achieved by the team at Waikato DHB was undone by the unfortunate and unauthorised actions of the former chief executive. The priority now is to get back to business as usual and for the board to support our interim chief executive and his wonderful team without any further distractions being played out publicly."
Simcock said he made the decision after considerable thought and reflection.
He had previously rejected numerous calls for his resignation saying he had done nothing wrong.
National's health spokesman Jonathan Coleman said the resignation of Waikato DHB chairman was inevitable and should have happened much sooner.
"Bob Simcock is a very good man, He's done a great service but I think there's an air of inevitably since the widespread publication of what has gone on there with unauthorised expenditure by the former chief executive. I think it was pretty clear that Bob had to go and I'm sorry he has had to in these circumstances because he is a good person and has been a very good DHB chair.
Coleman said he received a written question from Clark yesterday where he was told he had not asked for a written resignation from the chair of the Waikato DHB or any DHB chairs.
"What really surprises me is the minister of Health has sat on this for so long.
"I would have thought in these circumstances the minister would have acted earlier and much more decisively because it is quite clear in this situation that the chair has to go. So I think David Clark has been pretty indecisive on this.
"The point is this has been around for weeks and weeks. The chief executive resigned on October 5 – David Clark was sworn in over a month ago. This has widespread publicity. I think he should have taken decisive action far earlier."
Coleman was reluctant to challenge his governance, saying Simcock was put in a challenging position by the former Waikato chief executive Nigel Murray.
"Bob has had a long and distinguished career, but quite clearly he's been dealing with a difficult situation here which I think many people chairing a DHB would have found difficult and no one expects a chief executive would undertake this amount of unauthorised expenditure. I think it was an unexpected situation and certainly would not have anticipated that the chief executive would have acted in that manner."
He also defended his own role in not removing him as chairman when he was Minister of Health saying the extent of the expenditure came to light during the election and when National was caretaker and unable to do anything.
Board member Dave Macpherson, who has repeatedly called for Simcock to resign, said the chairman had "done the right thing".
"It's the right thing to have happened, although it's a bit late."
Macpherson endorsed Sally Webb, the deputy chair, as the new chair and said he looked forward to the organisation moving forward.
Association of Salaried Medical Specialists executive director Ian Powell, who called for Simcock to stand down today following Herald revelations that the Serious Fraud Office was looking into Murray's expenses scandal, welcomed the news.
"It was just inevitable. Unfortunately Bob Simcock had no insight into everything. The appointment (of Murray), the behaviour, the absurdity of going to an American company (to provide a virtual health app) ...
"There are just so many ABCs that he got wrong."
Former Labour MP Sue Moroney, who warned Simcock not to hire Murray in mid-2014, said the decision by the chairman to stand down over the expenses debacle was "a long time coming".
"Disappointed that it's taken so long for Bob Simcock to do the right thing and resign for his lack of oversight of a CEO who was clearly taking the taxpayer for a huge ride."
Moroney said she was concerned with how people in "these positions of authority seem to hang on for grim life in circumstances that are clearly untenable long after it's become obvious that it's untenable for them to continue in those positions."
Simcock, who also chairs Waikato Regional Council's strategy and policy committee, failed to turn up to today's scheduled meeting and did not tender an apology. The deputy chair was also absent at the start of the meeting forcing the council's chairman Alan Livingston to step in.
